I. Field of the Invention
This invention relates generally to finishing assemblies and machines, primarily screeds and strike-offs for placing, screeding, finishing and shaping concrete. More particularly, the present invention relates to a self-propelled finisher that employs multiple rotating tubes to simultaneously propel the
machine while finishing, striking-off and screeding concrete.
II. The Prior Art
As recognized by those skilled in the concrete finishing arts, after concrete is initially placed during construction, the upper surface must be appropriately finished. The purpose of finishing is to give the concrete a smooth, homogeneous and correctly textured surface and appearance. Various finishing devices have long been in use throughout the construction industry for treating plastic concrete. Known prior art systems include "bull" floats, finishing boards, strike-offs, pan floats, plows, blades, rotary tubes and the like.
Generally, most concrete finishing assemblies employ a combination of the above devices to finish the concrete. Strike-offs are principally used to initially form and grade fresh concrete by contacting the rough, freshly placed plastic concrete with a leading edge. Screeds are normally elongated tools that employ a leading surface or blade that is moved over the concrete surface to finish it. These finishing assemblies may float on the concrete itself or they may ride the surrounding concrete forms. Modern finishing machines allow several finishing steps to be accomplished in a single pass.
During construction concrete may be poured between spaced-apart forms and then finished while still plastic. Typically, the freshly poured concrete is supplied in an excessive amount to insure that the resultant concrete slab is of the proper size and depth. Those skilled in the art will recognize that the selected finishing equipment must be appropriately matched to the job. In other words, the type of equipment must be chosen based on the condition of the concrete. For example, if high slump concrete is to be screeded, a floating pan would be ideal. For finishing drier concrete, a heavier twin-bladed screed might be more desirable. In all cases it is desirable to finish the concrete quickly and efficiently in a single pass.
The selection of an appropriate design for a particular finishing machine or assembly is also based upon a variety of parameters dependent upon the concrete involved. The characteristics of a particular batch of concrete depend upon the type and percentage of aggregate, and the quality and quantity of sand, cement, ad-mix, water and chemical additives used to formulate the concrete. Other variables, such as temperature, slab thickness, slump and placement method also affect the finishing assembly selection and the application procedure.
A particular problem the excess concrete commonly used in most projects causes is that it often makes ordinary form riding rotary tube finishers "ride up" on top of the concrete. Another problem results from the fact that concrete poured by the delivery truck is concentrated in one area and must be spread out. Extreme surface irregularities in unfinished areas result. In effect, large bumps and extremely unlevel regions in the concrete surface arise. Bumps can cause finishers to "ride up." If the finisher drive rollers "ride up," they lose contact with the forms. When the rollers do not contact the forms, they no longer finish the concrete surface correctly and are unable to continue independent movement. Thus, some of the excess, freshly poured, unlevel plastic concrete must normally be displaced away from the finisher.
I hold several patents in the art of concrete placement and finishing. The most relevant is U.S. Pat. No. 4,702,640 that teaches a single roller concrete finisher that utilizes a pair of cooperative end handle assemblies. This single roller system is directed at finishing concrete upon sloping surfaces.
My U.S. Pat. No. 4,349,328, teaches a self-propelled "triangular truss" screed that rides upon forms U.S. Pat. No. 4,798,494 discloses a floating vibratory screed that finishes concrete with or without forms.
Finally, U.S. Pat. Nos. 4,316,715, 4,363,618 and 4,375,351 and the various references cited and discussed therein are germane to the general technology discussed herein. All the above patents have been assigned to the same assignee as the present case.
U.S. Pat. No. 4,142,815, issued Mar. 6, 1979, to David Mitchell teaches a rotary tube finisher that is adapted to rotate counter to the directional movement of the finisher. This patent does not teach a reliable method of finishing the concrete in a single pass. This device also fails to provide a vertical adjustment for the movement of the rotary tube relative to the supporting forms.
Other prior art screeds, generally of the "form-riding" type, that are of general relevance include those screeds disclosed in U.S. Pat. Nos. 4,340,351; 4,105,355; 2,651,980; 2,542,979; 3,095,789; 2,693,136; and 4,030,873.
The prior art has failed to adequately address the "riding up" problem associated with the use of rolling tube finishers. Many of the prior art finishers fail to effectively finish freshly poured plastic concrete in a single pass. Furthermore, the prior art fails to teach an efficient method of displacing excess, unlevel concrete to maintain drive roller contact on self-propelled form riding concrete finishers. The prior art also fails to provide an adjustable, integral strike-off roller that is vertically adjustable to vary the depth of the concrete adjacent the drive rollers.
Ideally, a finishing machine would use a plurality of rollers to compress the concrete while also preventing "riding up." It would also level or grade and displace excess, unlevel concrete away from the front or leading edge of the finishing machine.
Thus, it is desirous to provide a finishing machine that will finish freshly placed plastic concrete effectively in a single pass. The device should be self-propelled, and it must be able to effectively strike-off excess concrete adjacent the leading edge of the machine. An acceptable machine must not "ride up" over the concrete and loose motive contact with the forms.